Armed confrontations over the Jordan date to the founding of Israel in 1948 and the recognition that sources of the country's needed water supply lay outside its borders. Its survival depended on the Jordan River, with its headwaters in Syria and Lebanon, its waters stored in the Sea of Galilee, and the tributaries that flow into it from neighboring countries.

Israel's neighbors face a similar situation. Their survival is no less at stake—which makes the line between war and peace here very fine indeed. In the 1960s Israeli air strikes after Syria attempted to divert the Baniyas River (one of the Jordan's headwaters in the Golan Heights), together with Arab attacks on Israel's National Water Carrier project, lit fuses for the Six Day War. Israel and Jordan nearly came to blows over a sandbar in the Yarmuk River in 1979. And in 2002 Israel threatened to shell agricultural pumping stations on the Hasbani, another of the headwaters in southern Lebanon.

Yet fights over water have also led to dialogue. "There are few major sources of water that don't cross one or more political boundaries," says Gidon Bromberg, the Israeli co-director of Friends of the Earth Middle East. "That creates a natural interdependence between countries." Sharing resources can actually be a path to peace, Bromberg says, because it forces people to work together. In the 1970s, for example, Jordan and Israel agreed on how to divvy up water even when the countries were officially at war. And cooperation between Israelis and Palestinians over water has continued even as other tracks of the peace process hit a wall.

"It seems counterintuitive, but water is just too important to go to war over," says Chuck Lawson, a former U.S. official who worked on Israeli-Palestinian water issues in the 1990s. "Regardless of the political situation, people need water, and that's a huge incentive to work things out."

One day last April, Bromberg led me to the natural spring that provides water to Auja, a Palestinian village of 4,500 people that climbs the barren hills a few miles west of the Jordan River near Jericho. Fed by winter rains, the spring was flowing from a small, boulder-strewn oasis, and we trekked along the narrow concrete trough that transports water to the village, several miles away. "Auja is totally dependent on this water for agriculture," Bromberg said. "As soon as this spring dries up, there'll be no more water for farming."

Part idealist, part political operative, Bromberg was born in Israel and raised in Australia, then returned to Israel in 1988 to help build peace in the region. By challenging his own country to share water equitably, Bromberg has rattled the cages of hard-line Israeli politicians who see water as a national security issue—and as a resource to guard jealously.